Finishing of polyamide fabrics



Dec. 26, 1944. E B, BENGER 2,365,931

FINISHING OF POLYAMIDE FABRICS Filed Feb. 13, 1941 l @P1 l Jweilz'ny Bai/b f.. .F) W

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EF1-MEST EIBEEEP Patented Dee, 26, l1944 FINISHING 0F POLYAMDE FABRICS Ernest B. Bengel', Wilmington, Del., assigner to E. I. du Pont de Nemours & Company, ton, Del., a corporation of Delaware Wilming- Application February 13, 1941, Serial No. 378,835

9 Claims. (Cl. 8-136) invention relates to textile fabrics and more particularly to a process for improving the resilience of fabrics prepared from synthetic linear polymer fibers.

t 'I'he fabrics with which this invention are concerned are prepared from fibers made of synthetic linear polyamides of the general type described in U. S. 2,071,250; 2,071,253 and 2,130,948. These polyamides are high molecular weight polymers which are generally crystalline in structure and which are capable of being cold drawn into fibers A showing by characteristic X-ray patterns molecular orientation along the liber axis. Generally speaking, these synthetic linear polyamides comprise reaction products of a polyamide-forming composition in which the y'molecules are bifunctional and contain two amide-forming groups, each of which is complementary to an amide-forming group in other molecules in said composition.

The polyamides defined above or as otherwise identified hereinafter can be obtained, for example, by self-polymerization of monoaminomonocarboxylic acids, or by reacting diamines with dibasic carboxylic acids in substantially equimolecular amounts, it being understood that reference herein to the amino acids, diamines,`

and dibasiccarboxylic acids is intended to include the equivalent amide-forming derivatives thereof. In the case of the amino acids these derivatives include substances such as the ester, amide, lactam, n-formyl derivatives, and, when water is present, the nitrile; in the case of the diamines they include the carbamates and the N-formyl f and N,N'diformyl derivatives and in the case of the dibasic carboxylic acids they include the diester, monoester, anhydride, amide, acid halide, and, when water is present, the monoand dinitriles. These polyamides include also polymers obtained by including with the polyamide-forming reactants other linear polymer-forming reactants, e. g., glycols, monohydroxymonocarboxylic acids, and monoaminomonohydric alcohols. It should benoted that in the polyamides of this invention the amide group is an integral part of the main chain of atoms in the polymer and in the case of the preferred polyamides the average number of carbon atoms separating the amide groups is at least 2.

It is known that synthetic linear polyamides of the above type yield strong fibers of good elasticity. Ihese properties have been largely responsible for the commercial success of these ibers in knitted fabrics, particularly full fashioned stockings. vWoven fabrics prepared from these fibers have thus far shown little promise because they have poor hand and are deficient in resilience, that is,they do not have the life or springiness of fabrics made from natural bers such as silk andwool. They are also deficient. in hand and drape. It is also known that fabrics made from nat ural fibers, such as cotton, silk and wool, and from articial cellulosic fibers are given finishing treatments which improved their hand, appearance, and other properties. Such treatments comprise subjecting the fabrics to the action of warm or hot soap solutions with or without various mechanical treatments. Application of such treatments to the synthetic linear polyamide fabrics produces little or no improvement in resiliency or hand.

lt has been proposed to improve the properties of synthetic linear polyamide fabrics by steam treatment. While such treatment does improve the ability of the fibers to recover from deformation and, when applied to fabrics, decreases their tendency to wrinkle, it bringsabout only a small improvement in the resilience of the fabric. Furthermore, the process requires a long treatment and therefore does not lend itself to continuous operation.

An object of this invention is to bring about a permanent improvement in the properties, parti cularly in the resilience, of fabrics prepared from synthetic linear polyamide fibers. Another ob- `ject is a new `and improved process for setting `a fabric comprising synthetic linear polyamide fibers is uniformly heated for a short time to a temperature closely approaching the fusion point of the fibers. To eifect rapid transfer of heat to the fabric and to minimize the danger of oxidation, the fabric is most advantageously heated by bringing it in contact with a heated surface. To obtain a uniform product, the fabric as originally treated must be uniform with respect to its content of moisture or other swelling agents.

The term ber is used herein to include both short (staple) and long (continuous) laments.

The process of this invention is most advantageously applied at that stage in the processing of they fabric where finishing treatments would described with reference to such fabrics. While.

the process may be applied directLv to the fabric as it comes from the loom, it is preferably applied to the fabric after it has been given a washing or boil off treatment. Such prior treatments serve to remove yarn sizes, oils. etc., which may be required in the weaving processes. Under the boil off conditions, the weave of the fabric is not set, or at least only partially set. so that the fabric is left in a. favorable state for application of the present process.

After the fabric has been washed it is put in condition for the heat treatment. If the fabric is to be treated in the moist condition, the fabric is run through squeeze rolls or the like to remove excess water. This will give a fabric of uniform moisture content which can be heat treated directly. On the other hand, if it is desired to treat the fabric dxy or to incorporate specific amounts of water or other swelling agents. the fabric is dried or partially dried and the desired amount of swelling agent added. It is essential that the fabric be uniform with respect to water content or content of other swelling agents, plasticizers and the like, if a uniform effect is to be produced in the heating operation. v

The heating operation consists in bringing the fabric for a short time to a temperature closely approaching the fusion point of the fabric. This is preferably done by passing the fabric over a heated surface or between two heated surfaces under pressure since this brings about almost instantaneous heating of the fabric to the desired temperature and avoids long exposure to heat such as occurs when the fabric is heated in an oven. As willbe more fully explained hereinafter, the temperature towhich the fabric is heated will depend upon the melting point of the polyamide, the amount of water or other modifying agent present, and the mannerin which the heat is applied.

Fig. 1 is a, diagrammatic view in elevation of one form of apparatus for carrying out my invention, and

Fig. 2 is a similar view of a modified apparatus.

'I'he fabric and the heated surface can be brought' in contactby various methods. Although the fabric can remain stationary and the heated surface moved over the fabric, it is generally more convenient to draw the fabricA across the heated surface. Thus the fabric can be carried past the heated surface by means of a belt, or can be drawn or carried over a heated roll or rolls with or without pressure being maintained on the back of the fabric. Likewise the fabric can be heat treated by a roll pressing the fabric against a heated shoeor by numerous other devices.

In the process as carried out by the mechanismof Fig. 1, the fabric after being given a preliminary boil off to remove the size and oil used in `weaving is rinsed free of soap. dyed if desired, and wound on the supply roll S either before or after drying. depending upon the condition in which the fabric is to be procemed. If the fabric is to be processed i. e. in with air at a denite humidity, the fabric is air dried before winding and the fabric brought to equiliba,ses,os1

rium with the air on the roll. If the fabric is to be heat treated in the wet or damp state. it can best be wound on the supply roll before drying, thus avoiding the necessity for subsequent water treatments. For treatments with swelling agents, the fabric is preferably dried before such treatments to insure uniform and controllable take up ofthe swelling agent. For prolonged contact of swelling agent with fabric, the fabric ls best passed through the swelling bath before Winding on the supply roll, and then allowed to remain on theroll for some time to insure uniformity. When ready for heat treatment, the supply roll S containing the fabric is placed in the position shown in the drawing. If the fabric is to be treated as such, the bath B is omitted, the fabric being passed directly over the guide Ge and between the rolls P1 and P2 to the wind-up roll W. Either one or both of the rolls P1 and Pz are equipped so that they may be heated and their surfaces maintained at an accurately controlled and uniform temperature. 'Ihe fabric is carried through the equipment by synchronized driving mechanism on the heater rolls Pi and/or'Pz and the Wind-up roll W. If the fabric is to be treated with a liquid prior to the heat treatment, the bath B is used. the fabric lbeing runl under the guides G1 and Ga. If desired, the bath can be replaced by a spray or other device for applying the liquid uniformly to the fabric. It is desirable that one of the rolls Pi or Pz have a surface of a soft porous structure, for example, a heavy fabric. The type of equipment shown in Fig. 1 is particularly desirable where high pressures'are applied to the fabric and where extremely brief contact times are desirable. Greater contact times of fabric with heated roll can be maintained without reduction in roll speed by raising the position of the guide Gs, to give a larger area of contact with the roll. This has the further advantage that the fabric is largely shrunk before passage through the rolls which lessens the tendency for wrinkling to occur between the rolls.

The equipment illustrated in Fig. 2 is identical with that shown in Fig. 1 except for the means for applying heat and pressure to the fabric. The heating .and pressing are accomplished by passing the fabric between the roll H and the split cylinder or shoe P. 'I'he split cylinder makes pos.-l

sible the application of suicient pressure to insure adequate metal to fabric contact. The equipment may be arranged so that either the roll or the cylinder or both can be maintained at a uniformly controlled elevated temperature. As in Fig.' 1, the bath B can be eliminated or a spray substituted for, it.

The heat processedfabric may, if desired, be washed or `treated with special finishes before submission to the trade. Such treatments or nishes are, however, merely supplementary and contribute no fundamental changes to the processed fabrics, which have been permanently im proved by the basic process of this invention. In cases where the heat stability of the nnish permits, the finish can be applied before the fabric is subjected to the heat treatment of this invention.

The invention is illustrated more specically in the following examples.

EXAMPLE I A satin fabric woven from polyhexamethylene adipamide yarn (M. P. in air about 250' C.) was boiled off at 70 C. in a dilute soap solution to remove the size, oil, etc. used in the weaving to reach equilibrium in an atmosphere of 85% vrelative humidity. The fabric was next heat proc'- :5,305,931 operation. The fabric was then dried and allowed means of a surface maintained at a temperature between .210 and 240 C. was of good appearance, hand. drape. and resilience. The crease angle ofthe treated fabric was which was 02%' less than that ofthe original fabric.

good hand, resilience and drape. A similar fabl0 ric, processed at 200 C., also had satisfactory properties, whereas one processed at 150 C., while superior to the above satin fabric, was stili to be' classed as an unfinished produc Measurement of "the crease angle" of a'. fabric serves as a quantitative measure of its resilience.

The crease angle is determined by folding a one inch square of fabric so that in separate tests both the warp and filling threads are bent through 180, placing a l kilogram weight on the folded fabric for 1 minute and measuring the angle to which the fabric recovers 30 seconds after removal of the weight. The crease angle is the angle which l the fabric lacks of flattening out, the smaller the crease angle the better the resilience. Resiliences of the above satin fabrics in terms of the crease angle, as determined by this method, are given below. *l

Benzyl alcohcl,..a high boiling liquid dissolves polyamides at its boiling point (205 C.) but when usedin aqueous solution (preferably less than 5% benzyl alcohol) is eilective in promoting setting of polyamide, fabrics at lower temperatures than possible without the active agent. .The quantity of lsolvent used is insufficient to dissolve the fibers, yet suiiicient to render them fusible at somewhat lower temperatures. Likewise eective are other solvent or swelling compositions, such as aqueous or alcoholic solutions of phenols, glycols, acids, alcohols, and the like. Whereas alcoholsand phenols tend to produce softer fabrics of improved drape. ,the more active acids, such as formic, tend to give a crisper feeling product. Swelling compositions are particularly edective when it is desirable to uselower heating temperatures or in refinishing fabrics previously heat set where the added softening eect of the solvent enables the fibers to be more readily reset than when dry or water saturated.

l EXAMPLE IV C Perma@ 3 The following table gives the results obtained Tempel-stummen treatment am? megf by bringing a moist polyhexamethylene adipansle amide fabric in contact with a uniformly heated smooth surface unde a pressure of about 2 Degrees v Nootzf'geatment (control) 6g 35 pounds per sql'lavre inch QIIIIIIIIIIIIIIIII ,..III 1s 1o Y Table! The treated fabrics of this invention are dissurface Contact crease tinguished from like fabrics not receiving the sample tm". ms angle Remarks present treatment by a greater resilience. Although the resilience depends somewhat upon the 210 12 34 F bri t th fabric structure, the treated fabrics of'this inven- A- hagedf "mg u tion for -the most part have a crease angle, as l ,1g fg 42g: defined above, of less than 25. '23ol 12 1s Do.

While a difference in crease angle` of a few 6 3g Bg: degrees may seem small, it makes a significant 24o 12 Fabric damaged. difference in the hand of the fabrics. A marked difference in resilience exists between the fabrics treated at 200 C. and 240 C., and a great dierence between the fabrics treated at 150, C. and 240 C. The preferred temperatures for treatment, under the above conditions lie be tween 220 and 245 C.

EXAMPLE II A fabric prepared from90 denier, 30 filament 70 polyhexamethylene adipainide yarn woven with 103 warp and '7l filling ends per inch was desized 'by agitation in lukewarm water and air dried. Thisl fabric, when soaked or dipped in a At the pressure indicated the optimum surface temperature lies between 220 and 235.C. At this temperature a contact time of 6 seconds is suiiicient.

EXAMPLE V A moist fabric of polyhexamethylene adipamide, while supportedon a canvas belt, was

drawn over a stationary roll heated to 260 C.

6r been shown in the previous examples where relatively low pressures (2 pounds per square inch and less) were used to promote contact of the fabric with the heated surface. When high pressures are used, the temperature is more critical, particularly when the fabric contains a swelling agent. With high pressures lower temperatures -must`be used and the times of contact must be extremely brief as is illustrated in the following example where the effect of pressure is particusaturated.aqueous solution of benzyl alcohol and 'I5 larly'consldered.

then nested uniformly over its entire width 'by ExnuLa VI A woven polyhexamethylene adipamide fabric was soaked in water. superiicially dried to remove surface water, and then pressed under high pressure against a heated copper surface for an accurateLv timed period. The results obtained by treating several samples of fabric in this manner showed -that the best results were obtained at a temperature of about 200 C. with a contact time of 0.1 to 0.2 second. Longer contact at this temperature resulted in a weakening of the fabric. The crease angles of the products treated for 0.1 to 0.2 second ranged from 15 to 11. In contrast a like fabric treated in an autoclave for 4 hours in saturated steam at 140 C. had a crease angle of 25. It should be noted that the present treatment is accomplished in a very small fraction of the time required for the steam treatment and produces a greater improvement.

EXAMPLE VII A fabric was woven from yarn spun from a polyamide (M. P. in air about 285 C.) derived from p-bis (beta-aminoethyl) benzene and sebacic acid. After the fabric was soaked in water to remove the size and given a boil-off with 2% soap solution, the moist fabric was effectively treated by bringing it in contact for seconds with a plate maintained at 250 C. The finished fabric had a crease angle of as compared to 54 for the original desized fabric.

EXAmLr: VIII A sample of polyhexamethylene adipamide yarn l is woven into a fabric with a 120 X '70 construction. The fabric is given a boil-off treatment and is then wound on a receiving roll. The fabric is unwound from this roll, passed under a guide roll partially submerged in a trough of water, and then passed between two heated pinch rolls. After passing through the pinch rolls, the fabric is collected on a wind-up roll. The pinch rolls are electrically heated to a temperature of 195 C. and thermostatically controlled so that the temperature of the rolls remains within the range ISO-200 C'. The pressure between the rolls is adjusted to givegood roll-to-fabric contact. The wind-up roll is driven at such a speed that the fabric passes through the pinch rolls at a rate of 4 yards per minute.

The crease angle of the finished fabric was 18 as compared with 45 for the fabric after the boil oi.

.a finishing treatment in accordance with Ex- -a-mple VIII by unwinding the fabric from the roll, passing it through a trough of water, and

then between two heated pinch rolls. The fabricv is found to have a. markedly increased resilience over that of a sample of the same fabric which was subjected to a conventional wool fabric nnishing treatment.

EXAMPLE X -Polyhexarnethylene adipamide is spun from melt into a 116 denier, 10 filament yarn. This yarn is doubled into a rope of approximately 11,600 denier and is then -colddrawn approximately 400% (ratio of drawn to undrawn, 4:1) to produce a drawn rope of approximately 3,000 denier. This rope is then crimped by a gear crimping process which consists in pressing the superpolyamide filaments between intermeshing serrated racks and heating them in this .position with steam, preferably saturated steam at 1D0-150 C. The function of the steam is to make the crimp more permanent. The crimped filaments are then cut into staple, spun into yarn, and woven into a fabric suitable forthe'vproduction of a. mans suit. The fabric is then finished at 240 C. in accordance with the method described in Example I. The fabric has a markedly better resilience than a, similar fabric processed at C.' When converted into a mans suit, the fabric maintains aysmart, neatly pressed appearance even when subjected to rough use; whereas a similar fabric which has only been finished according toa conventional wool fabric finishing method becomes wrinkled .very easily and does not exhibit a resilience even approaching that of the fabric finished in accordancewith this invention.

- EXAMPLE XI v A sample of dyed satin fabric woven with 30 denier warp-40 denier filling thread structure was decatized by standard mill processes. The fabric, was, considered unsatisfactory by the trade.- When -this fabric was'treated in the air dr'y condition for 5 to 10 seconds at 230 C. vby

the process of Example I, its hand, drape, ap-

lpearance and resilience were markedly improved. The product was considered acceptable by the trade.

From the foregoing examples it will be seen 'that the resiliency of polyamide fabrics is greatly definitely, it is believed that the treatment of this invention softens (without fusing) the fibers sufficiently to relieve strains introduced in the fabric during weaving and that this is responsible, in part at least, for the improvement in properties. It is believed further that the treatment sets the yarns in this relaxed condition which is in conformity with the desired weave pattern of the fabric. Examination of nished fabric shows that both the warp and lling yarns have taken on a permanent set. At the points of intersection in the weave the yarns are set in the form of humps. This permanent setting of the yarns in conformity with the weave 'appears to be essential to good fabric properties.

The process is preferably applied before the fabric is formed into garments or sold to the trade since untreated polyamide fabrics are particularlyysubject to weave distortion, permanent wrinkling, creasing-and the like. However, due to the fact that the treatment of this invention makes it difficult to form :sharp creases in the nished fabric, garments in which sharp and permanent creases are of prime importance may be made from untreated fabric. and the heat treatment applied to the garment. In this way shaped or formed articles of apparelcan be formed from the fabric. f

As compared. with. the finishing treatments which are applied to fabrics made from other types of fibers, e. g. silk, wool and rayon, the

treatment herein described for the polyamide fabrics isunusually severe with respect to the temperatures used. The process of this invention, when applied to fabrics of these other types of fibers, do not have the beneficial effects they do in the case of the Vsynthetic polyamide fabrics.

The process of this invention is further characterized in that its effect is essentially permanent. Subsequent treatments, such as fabrics receive in further processing and use, e'. g. hot

dyeing and laundering, do not destroy the bene-v flcial effect of the finishing treatment. The effect is permanent even at elevated temperatures. For example, if a sharp crease is introduced into a polyamide fabric by the lprocess of this invention, this crease persists through laundering and is not completely removed even by ironing. In contrast creases in similar silk or wool fabrics are completely eliminated-by washing and ironing. `With further reference to the severity of the conditions in the process of this invention, it may be pointed out that although the fibers undergo shrinkage they retain their orientation. However, there may |be some change in the ber structure since the dyeing properties of the fabrics are altered by the process. The nished fabrics dye uniformly but less deeply than untreated fabrics, both with acid and Celanthrene type dyes.

In the foregoing examples the polyamide fabrics were pretreated in various ways before they were subjected to the heating operation. For wet treatments it is oftenl desirable to soak the fabric in water for several hours before the heat treatment, removing the excess surface moisture just before applyingl the heat treatment. It is also permissible to boil the fabric for a brief period in water, soap solutions, or other textile processing baths including the milder swelling baths prior to the flnishingtreatment. It has been found that boiling the fabric in an aqueous solution of a water-soluble polyamide, e. g. that derived from triglycoldiamine' and adipic acid,

serves to give a fabric which nishes particularly well in the subsequent heat treatment. `This is apparently due to impregnation of the fabric with the lower boiling water-soluble polyamide. It is frequently advantageous to partly preset a polyamide fabric by plunging it into boiling water or soap solution while maintaining the fabric smooth and to its full width, since this presetting serves to minimize wrinkling, creasing, or detorsion of the fabric in any subsequent operations carried out prior to the final heat treatment. Although these pretreatments in themselves have some setting effect on the fabrics, they do not interfere with the subsequent treatment of this invention which is carried out at a much higher temperature.

'Ihe nish desired on the ultimate fabric determines to a considerable extent the pressure to be used in contacting the fabric with the heated surface. In order to obtain soft fabrics, low pressures are necessary, pressures of from a fraction of a pound to several pounds per square inch being most effective.

While the invention is most advantageously applied by treating the fabric on a heated surface since this process insures rapid heat transfer and does not contaminate the fabric, some degree of success has been achieved by heating the fabric in other ways. For example, the fabric may be passed through a hot inert liquid or the fabric may be passed through ay zone in which it is heated by infra red radiations.

The temperature used in the heating step will V excessive.

generally be within about 5 to 25 C. of the teln- .perature causing fusion or visible damage to the fabric. Tue temperature employed in a given case depends upon the particular polyamide from which the xabric is made, the amount, if any,A

of Water or other swelling agent present in or on the bers, and the pressure applied to the fabric. Thus, for dry fabrics 'made from poly hexamethylene adipamide, winch melts at about zoo C. on a metal block in air. plate or suriace temperatures in the neignbol hood of 2am-2gb C. are particularly -elfective when pressures in the neighborhood of one pound per square inch. are used. For polydecametriylene adipaliiiu'e fabrics, which melt at about Z'b C. the temperature should `be correspondingly lower. When the fibers contain swelling agents. lower iimsning temperatures are employed than in the absence of swelling agents. since tneswelling agent lowers the fusion point of the fibers. Forexample, under pressure polyamides become soluble in water at temperatures well below the melting point of the dry polymer. The actual melting point lowering depends upon the moisture content of trie polyamide and Ior certain polyamldes may amount to o0 C. In heating a Water saturated fabric two phenomena Whlch'occur are a gradual elimination 0f water and a gradual rise in the temperature of the moist fibers. rate of heating is not too rapid, the water can be removed before the polymer melting point is reached and temperatures within about o C. or' the dry polymer fusing point can be used safely. 'If heat is rapidly applied. as by contacting the fabric with a heated surface or plate under considerable pressure, plate temperatures as much as tu C. -below the dry polymer fusing point may'be For polyamide fabrics containing other swelling agents, which include y certain compounds per se, particularly non-solvents containing hydroxyl groups, and also mixtures of polyamide solvents and non-solvents, the behavior is similar to the effect with water except except tnatf'or the less volatile or more active agents slower rates of heating or lower temperatures must be used. Plate temperatures about 5-2U C. below the fusion point of the fabric are most effective. It should be noted, however, that these temperatures, depending upon the pressure applied during the treatment and the nature and amount of the swelling agent, may range from about 20 to 70 C. below the melting point of, the dry polymer. However, it is essential that the temperature employed be maintained uni- Y formly over the heated surface with a maximum fluctuation not exceeding 1u C. if trulyvuniform products are to be obtained. Furthermore, in order to obtain the full advantage of the process -of this invention. conditions should be chosen so that the temperature of the heated surface can be C. or higher. For this purpose all of the polyamides disclosed herein have melting or fusion points of at least 200 C.

The time of contact between the fabric and the heated surface should bes'uicient to bring the fabric to the desired temperature but insufficient to permit significant damage to the fabric by oxidation. The time of contact will generally be less than one minute and in most `cases from a fraction of a second to 15 seconds. Maximum changes in fabric properties occur during the first few seconds of heating with but slight additional improvement over the next minute. In the case of fabrics which are particularly sensitive to oxygen, it is desirable to eifect the nish- Ifthe' ing operation in an inert atmosphere, e. g. nitrogen or carbon dioxide. Although there is considerable latitude in the conditions of temperature, pressure, and time of contact which can be employed in the finishing treatment, it' will be apparent that these variables` are interdependent. Furthermore, it should be emphasized that it is very important that the'temperature, pressure, and timeof treatment be kept essentially constant during the treatment of a given piece of fabric if a uniform product is desired.

Polyamide yarns and fabrics shrink extensively on heat treatment, the amount of shrinkage de` pending upon the initial condition of the fabric, i. e. whether dry, moist with water or other swelling compositions, and on the rate and method of heat application. Io eliminate serious future shrinkage, and give a smooth uniform fabric homogeneous in physical properties, it is essential that heat be applied uniformly over the full width of'the fabric and that the fabric be uniform with respect to content of water or other swelling composition. Failure to apply the heat treatment simultaneously and uniformly over the full width of the fabric leads to an unsatisfactory product. When the heat treatment is applied over only a portion of the Width of the fabric the moisture content and other properties of the fabric change through a sharp gradient at the junction of the heated and non-heated portions. 'This causes puckering of the fabric due to shrinkage of the heated area. A second heat treatment overlapping the first fails to removed amples of polyamides may be mentioned polytetramethylene suberamide, polytetramethylene sebacamide, polypentamethylene adipamide, .polyhexamethylene sebacamide, polydecamethylene p-phenylene diacetamide, poly-p-xylylene sebacamide, and G-aminocaproic acid polymer.

The term polyamide as used herein includes interpolyamides and also interpolymers which contain other Alinkages in addition to amide linkages, such as those obtained by including with the polyamide-forming composition from which the polymer is prepared other linear polymerforming reactants. Examples of polyamides of this kind are the ester-amide interpolymers.

It is not necessary that the fabrics consist solely of polyamide bers. The fabrics may be prepared from yarns containing other fibers in addition to polyamide bers or from polyamide yarns and other types of yarns. The other bers or yarns should, however, have suiiicient thermal stability to withstand the finishing treatment.

The best results are obtained with fabrics consisting largely of polyamide fibers. It is also possible to use fabrics made from two or more different polyamides or from fibers spun from a mixture of polyamides. The fabrics may be of the woven, knit or felt types.

The polyamide bers present in the fabric may contain modifying agents, such as plasticizers, e. g. phenols-or aryl sulfonamides, delusterants, e. g. titanium dioxide, pigments, extenders, fillers, dyes, resins, antioxidants, oils, and cellulose derivatives. The bers may be long, i. e. continuous, or short, i. e. staple bers. The bers may be crimped or uncrimped. When crimped bers are used, they may be the products of mechanical crimping processes, such as stuffer-crimping or such as described in U. S. Patent 2,197,896; or of spontaneous crimping processes, such as are described in U. S. Patent 2,174,878 and in copending applications Serial Numbers 183,922, now Pat. No. 2,287,099, 233,481, now Pat. No. 2,249,756 and 324,847 now Pat No. 2,296,202; or of bale-crimping processes, such as described in copending application Serial.No. 232,470 now Pat No. 2,217,113. The crimp may be rendered more permanent by a mild setting treatment with a hydroxylated non-solvent swelling agent. However, this is not necessary since the crimped fibers can be spun into a yarn and fabricated without losing an appreciable amount of their crimp.

This inventionl as will be apparent from the foregoing description, provides a rapid and economical process for improving permanent' the resilience, drape, and hand of fabrics prepared with the use of synthetic linear polyamide fibers. Although the process is a simple one, the operating conditions must he carefully controlled and for this reason the process is preferably applied as a finishing treatment to the fabric before it is submitted to the consumer and in all cases before it has left the hands of an experienced and properly equipped operator.

As many apparently widely different embodiments of this invention may be made Without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to trie specific embodiments thereof except as defined in the appended claims.

I claim: l

1. A process for treating fabric comprising synthetic linear polyamide bers having a fusion temperature of at least 200 GQ). set said fabric and impart thereto improved resilience and a crease resistance which are not destroyed by subsequent laundering and ironing, said process comprising a step in the manufacture of the finished fabric for submission to the trade which comprises heating the polyamide fabric uniformly and simultaneously over its entire width by pressing the fabric over its entire Width against a heated surface and under essentially constant pressure between the fabric and heated surface until the temperature of said fabric is at least 190 C. and within the range of 5 to 25 C. below the fusion point of said polyamide fibers,

' and discontinuing said heating before the fabric has been weakened substantially.

2. A process for treating fabric comprising synthetic linear polyamide fibers having a fusion temperature of at least 200 C. to set said fabric and impart thereto improved resilience and a crease resistance which are not destroyed by subsequent laundering and ironing, said process comprising a step in the manufacture of the nshed fabric for submission to the trade which comprises heating the polyamide fabric uniformly and simultaneously over its entire width by continuously passing the fabric over a heated surface with an essentially constant pressure of the fabric against the heated surface and with a time of contact of fabric and heated surface which heats the fabric to a temperature of at least 190 C. and within the range of 5 to 25 C. below the fusion point of the polyamide fibers.

l3. A process for treating fabric comprising synthetic linear polyamide fibers having a fusion treating said fabric with a swelling agent and then heating the treated fabric uniformly and simultaneously over its entire width by pressing the fabric over its entire width against a. heated surface and under essentially constant pressure between thefabric and heated surface until the' laundering, said process comprising the steps in the manufacture of the finished fabric for submission to the trade which consist of uniformly treating said fabric with water to bring the fabric ceeding one minute in close contact with a surface having a temperature between 220 C. and 245 C.

6. In a process for obtaining a fabric woven from synthetic linear polyamide bers having a fusion temperature Vof at least 200 C. and characterized by an improved resilience and a crease resistance which are not destroyed by subsequent laundering and ironing, the steps in the manufacture of the nished fabric for submission to the trade which comprise treating the fabric, after it has been removed from the loom, to remove the size, oils and the like, and then be- Y fore the weave in the fabric has been completely set, heating the fabric uniformly and simultaneously over substantially its entire width by pressing, the fabric over substantially its entire width against a heated surface and under essentially constant pressure between the fabric and heated to a uniform moisture content substantially below the saturation point, and then heating the treated fabric uniformly and simultaneously over its entire width by pressing the fabric over its entire width against a heated surface and under essentially constant pressure between the fabric and heated surface until the temperature of said fabric is at least 190 C. and within the range of 5 to 25 C. below the fusion point of said polyamide fibers, and tdiscontinuing said heating before the fabric has been weakened substantially.

5. 'I'he process set forth in claim 1 in which said polyamide fibers are polyhexamethylene adipamide bers and in which the fabric is heated in an essentially` dry state for a period not ex- 7. A fabric which comprises essentially poly amide fibers, and which has a crease angle of less than 25, and which is obtained by the process set forth in claim 1.

8. The process setforth in claim 3 in which said polyamide bers are polyheilamethylene adipamide fibers.

9. The process set'forth in claim 4 in which said polyamide bers are fpolyhexamethylene adipamlde bers.

ERNEST B. BENGER. 

